1. Field of the Invention
The present invention relates to an optical scanning unit and an image forming apparatus provided with the optical scanning unit, and more specifically, to a configuration of a member for arranging an optical part such as a laser diode at a desired position using an ultraviolet curable resin adhesive in an optical scanning unit. In particular, the present invention relates to a technology for arranging a laser diode in a laser scanning unit of an image forming apparatus such as a copier.
2. Description of the Related Art
An optical scanning unit that scans a laser beam is used for an image forming apparatus such as a digital copier, a laser printer, or a facsimile. When an image is formed in the image forming apparatus, after a photoreceptor is charged by a charging unit, writing according to image information is performed by the optical scanning unit and an electrostatic latent image is formed on the photoreceptor. The electrostatic latent image on the photoreceptor is then visualized by a toner supplied from a developing unit. The toner image visualized on the photoreceptor is transferred onto recording paper by a transfer unit and is fixed on the recording paper by a fixing unit, thereby obtaining a desired image.
A laser diode serving as a light source of the optical scanning unit is attached to a predetermined holding portion. As the holding portion, for example, a wall portion of a housing serving as a housing of the optical scanning unit is applied. In this case, such a configuration is employed that a laser diode holder provided with the laser diode is used and the laser diode holder is fixed to the above holding portion. For example, the laser diode holder is attached to an opening provided in the holding portion, and after three-dimensionally adjusting the position of the laser diode, the laser diode holder is adhered and fixed to the holding portion. In this case, by applying an adhesive agent so as to couple an outer circumferential surface of the laser diode holder and a wall surface of the opening of the holding portion, the laser diode holder is fixed to the holding portion.
Concerning a configuration for adhering and fixing a laser diode in an optical scanning unit, for example, Japanese Laid-Open Patent Publication No. 2005-176051 discloses such a configuration for attaching a laser diode to a laser diode holder that the laser diode is fallen into a part of a counterbore provided in an opening of the laser diode holder through an auxiliary member, and after adjusting the position of the laser diode, an adhesive agent is injected into a gap between the auxiliary member and the counterbore to fix the laser diode.
As described above, when fixing the laser diode holder and the holding portion using the adhesive agent, conventionally, by applying the adhesive agent so as to couple the outer circumferential surface of the laser diode holder and the wall surface of the opening of the holding portion, the laser diode holder is fixed.
However, when performing adhering and fixing with such a configuration, a phenomenon occurs that due to surface tension, the adhesive agent that is bridged between the outer circumferential surface of the laser diode holder and the wall surface of the opening of the holding portion has an hourglass shape and a center part thereof is constricted and thinned. In this case, stress is focused on the thinned center part of the adhesive agent so that adhesive strength may be reduced to be insufficient. In order to prevent such a phenomenon, it has been necessary to give required strength by increasing an amount of the adhesive agent or lengthening a time to irradiate an ultraviolet curing type adhesive agent with ultraviolet rays.